Allison Transmission launches electric hybrid propulsion system for bus and coach 28 August 2020

​Allison Transmission has launched a zero emission vehicle (ZEV)-capable electric hybrid system, the eGen Flex, as the initial product offering under its new Allison eGen brand.

eGen Flex provides bus fleets with full electric engine-off propulsion and accessory power operation capability. The technology is intended for zero-emission zones and depot operation, including when approaching, during, and leaving passenger stops for a quieter and healthier environment.

The eGen Flex electric hybrid system includes a new drive unit, inverter and rechargeable energy storage system. The drive unit includes a disconnect clutch that enables engine-off capability. The inverter has an innovative package improvement that reduces its footprint and weight. The inverter is now water ethylene glycol (WEG) cooled, which eliminates oil lines, decreasing installation complexity, reducing maintenance expense, and increasing uptime. The energy storage system incorporates lithium titanate (LTO) technology, said to significantly increase energy density, allowing for faster charging and enabling pure electric (engine off) extended range capability.

Two models are offered: eGen Flex and eGen Flex Max. The first, eGen Flex, will be similar in feature set and capability to the Allison H 40/50 EP electric hybrid propulsion system, but with the package enhancements summarised above. The second, eGen Flex Max, will offer fully electric propulsion for up to 10 miles, dependent upon duty cycle and accessory load requirements.

Increased Accessory Power 2 will be available with eGen Flex, and will be required with eGen Flex Max. This capability electrifies vehicle accessory systems, such as air conditioning and electric heat, allowing those accessories to operate at their optimal efficiency point, reducing emissions and strain on the engine. Allison is engaged with transit original equipment manufacturers (OEMs) and transit fleets to support a scheduled 2021 commercial release of eGen Flex.

Branden Harbin, managing director of global marketing at Allison Transmission, says: “We understand that fleets are reluctant to go all in on electrification at this early stage. That critical feedback from our customers is what inspired Allison to deliver this enhanced capability for coach and transit buses, effectively serving as a bridge solution between conventional fuel and full electric solutions. eGen Flex will enable transit fleets to evaluate electric capability and their electric range needs, while still having the peace of mind of a diesel range extender, whether needed for longer routes, for route flexibility, unplanned congestion on routes, or an inability to recharge due to power grid challenges.”

Launch customer is IndyGo, the Indianapolis, Illinois, USA transportation corporation, and diesel manufacturer Cummins, which will see the eGen Flex Max electric hybrid system integrated into three new IndyGo buses. In addition, IndyGo selected Allison’s H 40 EPTM electric hybrid propulsion solution to power a further 24 new Gillig buses where they will be paired with the Cummins B6.7 diesel engine.

William Dalrymple

Related Companies
Allison Transmission Europe BV

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